Effect of nifedipine on capacitive calcium entry in Jurkat T lymphocytes.
The effect of nifedipine-an antagonist of L-type calcium (Ca(2+)) channels-on capacitative Ca(2+) entry (CCE) was studied in Jurkat T lymphocytes. CCE was induced by a variety of treatments each of which depleted intracellular Ca(2+) stores. Cells were treated with thapsigargin, ionomycin, anti-CD3 antibodies, and phytohaemagglutinin, or pre-incubated in a Ca(2+)-free medium. Activity of CCE was evaluated with a Ca(2+)-free/Ca(2+)-readmission protocol, in Fluo-3 pre-loaded cells. Nifedipine inhibited CCE in a dose-dependent manner. CCE inhibition was not due to non-specific effects on K(+) channels. Nifedipine, did not induce any membrane depolarization, as revealed by measurements of the plasma membrane potential with the fluorescent probe bis-oxonol. Moreover, experiments done under depolarizing conditions (i.e. by substituting Na(+) with K(+) ions in the medium) revealed that nifedipine could inhibit capacitative Ca(2+) entry independently of plasma membrane depolarization. We also demonstrated the presence in our Jurkat T-cells of transcripts for Ca(V)1.3 (alpha(1D)) and Ca(V)1.4 (alpha(1F)) L-type Ca(2+) channels. Verapamil and diltiazem, two unrelated blockers of L-type Ca(2+) channels, were less inhibitory on CCE. Possible mechanisms by which nifedipine interferes with Ca(2+) entry in these cells are discussed.
Colucci
Angela
A
Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, Siena, Italy.
Giunti
Roberta
R
Senesi
Silvia
S
Bygrave
Fyfe L
FL
Benedetti
Angelo
A
Gamberucci
Alessandra
A
D000906:Antibodies / Q000494:pharmacology; D001693:Biological Transport, Active; D017252:CD3 Complex / Q000276:immunology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D002463:Cell Membrane Permeability; D003593:Cytoplasm / Q000378:metabolism; D004110:Diltiazem / Q000494:pharmacology; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D019169:Jurkat Cells; D008564:Membrane Potentials; D009543:Nifedipine / Q000494:pharmacology*; D010835:Phytohemagglutinins / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D000906:Antibodies; D017252:CD3 Complex; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D010835:Phytohemagglutinins; D015759:Ionomycin; D019284:Thapsigargin; D014700:Verapamil; D004110:Diltiazem; D009543:Nifedipine; D002118:Calcium